How to Install a Damper in Ductwork

Several tubes of flexible ducting in a pile.
What You'll Need
Damper with appropriate screws and nuts
Power drill
Duct tape
Electric damper
Instruction manual
Wire nuts
Wire stripper

A damper can control the flow of air in your ducts, changing the output to different levels of your home or different rooms as needed. In this way, you can better regulate the temperature, especially between summer and winter months. Do be mindful when you add a damper, though, as your home’s duct system should already have been designed with air flow for the entire home in mind, especially in newer homes. However, it is not too difficult to install an inline damper, and below are some step-by-step instructions you can follow to add one yourself.

Step 1 – Understand Terminology

It is a basic principal of science that hot air rises and cold air falls. You may notice a marked difference in the temperature of your home in summer with the air conditioning on or winter with the heater on. If, in the winter, your downstairs is far warmer than your upstairs, and conversely in the summer, a damper installed in your ducts can allow you to change the flow, cutting off air where needed and letting the natural flow of hot and cold air do the rest.

Both manual and electric dampers are available. With an electric one, you can install a timer so that it will open and close at various times during the day, allowing the air to pass at some times and not at others. This article will address the basic installation involved with the manual type, so for instruction on electric types, you should consult the manufacturer’s guide for your selected model. As always, when working with electricity, turn off the power at the breaker before beginning any work.

Step 2 - Clean Ductwork

Before working on your damper installation, it is not a bad idea to clean your ducts. Your ductwork may be trapping dust, dander, allergens, etc, and not only do you not want to be breathing this, but it can impair optimum air flow.

Step 3 - Determine Location for Installation

Look at your furnace and at the ductwork to figure out the best place for the installation. If you wish to put the damper on the upstairs line, then you will need to put the damper at the beginning of the duct.

Step 4 – Measure

After you determine where the duct is and where you wish to install the damper, measure the diameter of the duct. You will need the same size damper for it to fit properly.

Step 5 – Install Damper

Open up the duct work, and drill two holes on opposite edges of the tube. These holes should line up with the pre-drilled holes on the damper. Remove the fasteners from the damper, connect it to the duct through these holes and into the drilled holes, and tighten. Then, seal both sides with duct tape.

If installing a damper which works on electricity, be sure that where you install it is not inline with any water source or spray, and that you have all recommended materials before beginning. You will need the proper electric source in the home (consult manual as well as your home’s wiring for power), additional wire, wire nuts, wire stripper, etc. Follow all instructions included with your electric damper for proper installation, and ground your connections before you finish.

Step 6 – Adjust Seasonally as Needed

Now you can adjust your damper, using its manual or electric control, to divert the air to different parts of your home depending upon the season.